The Nernst glower is an obsolete device for providing a continuous source of (near) infrared radiation for use in spectroscopy. Typically it was in the form of a cylindrical rod or tube composed of a mixture of certain oxides such as zirconium oxide (ZrO2), yttrium oxide (Y2O3) and erbium oxide (Er2O3) at a ratio of 90:7:3 by weight. They operated by being electrically heated to about 2000 °C. Initially they required external heating because the material is an insulator at room temperature.